Arrangement for the production of a three-dimensional product

ABSTRACT

The invention relates to an arrangement for the production of a three-dimensional product, which arrangement comprises a work bench on which the said three-dimensional product is to be constructed, a powder dispenser which is arranged to apply a thin layer of powder onto the work bench to create a powder bed, an irradiation gun for transmitting energy to the powder so that melting of the powder takes place, the arrangement comprising a casing within which the pressure is reduced in relation to the atmospheric pressure and within which the work bench and the irradiation gun are located, with the powder dispenser, or a supply pipe connected to the powder dispenser, being arranged partially outside the casing.

TECHNICAL FIELD

The invention relates to an arrangement for the production of athree-dimensional product, which arrangement comprises a work bench onwhich the said three-dimensional product is to be constructed, a powderdispenser which is arranged to apply a thin layer of powder onto thework bench to create a powder bed, an irradiation gun for transmittingenergy to the powder so that melting of the powder takes place, thearrangement comprising a casing within which the pressure is reduced inrelation to the atmospheric pressure and within which the work bench andthe irradiation gun are located.

BACKGROUND ART

In, for example, U.S. Pat. No. 4,863,538an arrangement is already knownfor the production of a three-dimensional product by melting insuccession selected parts of a layer of powder applied on a work bench.The arrangement comprises a work bench on which the saidthree-dimensional product is to be constructed, a powder dispenser whichis arranged to apply a thin layer of powder onto the work bench tocreate a powder bed, an irradiation gun for transmitting energy to thepowder whereby melting of the powder takes place, means for guiding theradiation emitted by the irradiation gun over the said powder bed tocreate a cross-section of the said three-dimensional product by meltingparts of the said powder bed, and a control computer in whichinformation about a succession of cross-sections of thethree-dimensional product is stored. By melting selected parts of powderlayers that have been applied in succession, the three-dimensionalproduct is constructed. The control computer is intended to controlmeans for deflecting the radiation generated by the irradiation gun overthe powder bed according to an operating plan which reproduces apredetermined pattern. When the required areas of a layer of powder havebeen melted according to the operating plan, a cross-section of the saidthree-dimensional body has been created. A three-dimensional product iscreated by melting in succession cross-sections that are created insuccession in layers of powder that are applied in succession by thepowder dispenser.

The arrangement according to U.S. Pat. No. 4,863,538 is designed for themanufacture of three-dimensional bodies in various kinds of material,for example metal or plastic. With certain materials, however, problemsarise with unwanted side-reactions. An arrangement has therefore beendesigned which comprises a casing within which the work bench, powderdispenser and irradiation gun are arranged. Within this casing thepressure is reduced, so that a vacuum arises. In this way, sidereactions are avoided.

However, a problem has arisen associated with replenishing powder in thepowder dispenser. For replenishing, the vacuum chamber must be opened,powder replenished, the vacuum chamber closed and a vacuum createdagain. This procedure involves a stoppage in the manufacturing process.In addition, the product on the work bench is able to cool. This means,among other things, that the fusion of the different layers is impairedand that the next layer of powder can therefore adhere less strongly.Cracks can arise in the product.

There is thus a need to solve these problems associated withreplenishing the powder in the arrangement.

DISCLOSURE OF INVENTION

The problems described above are solved by means of the invention bymeans of the powder dispenser being arranged partially outside thecasing. This is arranged according to the invention by a part of thepowder dispenser being arranged outside the casing and another partinside the casing. In this way, powder can be added to the powderdispenser without the manufacturing process needing to be interrupted.

It has the same effect for the invention if a supply pipe is takenthrough the wall of the casing as when the powder dispenser is takenthrough the wall of the casing. An embodiment in which the powderdispenser is arranged inside the casing, but is connected to a supplypipe which is taken through the casing, is also covered by theinvention.

In order to help to prevent an increase in pressure, the arrangementaccording to the invention comprises means for preventing the powderdispenser's contact with the surroundings affecting the pressureconditions inside the casing. The means for maintaining the pressureconditions inside the casing can, for example, be a column of powderinside the powder dispenser. Another means for maintaining the pressureconditions within the casing is to provide the powder dispenser with acover with a valve. Such a cover with valve can, for example, bearranged on the top or at the bottom of the powder dispenser. It is,however, important in order for the pressure conditions inside thecasing to be maintained that, when in use, the powder dispenser hasconstantly a column of powder of a certain height. The column of powderhas preferably a height of 1000 mm. A 1000 mm high column of powder issufficient to maintain the pressure conditions for a column of powderwith a diameter of approx. 140 mm when the powder has a particle sizethat fulfils the following parameters. No particle has a diameter thatexceeds 106 μm. Only a few particles have a diameter that is less than40 μm. The majority of the particles (more than 50%) have a diameterthat is 80 μm.

According to an embodiment of the invention, the arrangement comprises afirst chamber, which encloses the work bench, and a second chamber,which encloses the irradiation gun, the chambers being located insidethe casing and connected to each other via a duct. The powder dispenseris preferably arranged in association with the first chamber.

According to an embodiment of the invention, the arrangement comprises ameans of supply in the form of a container with compartments which canbe moved so that powder can be supplied to the powder dispenser from thedifferent compartments.

DESCRIPTION OF DRAWINGS

FIG. 1 shows an arrangement according to an embodiment of the inventionviewed in cross-section.

FIG. 2 shows an arrangement according to an embodiment of the inventionviewed in cross-section.

FIG. 3 shows the embodiment according to FIG. 2 from a differentviewpoint.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows in cross-section an arrangement for the production of athree-dimensional product generally designated by 1. The arrangementcomprises a work bench 2 on which a three-dimensional product 3 is to beconstructed, a powder dispenser 4, and a device 28 which is arranged toapply a thin layer of powder onto the work bench 2 to create a powderbed 5, an irradiation gun 6 for transmitting energy to the powder bedwhereupon melting of parts of the powder bed takes place, means forguiding 7 the radiation emitted by the irradiation gun 6 across the saidwork bench to create a cross-section of the said three-dimensionalproduct by melting the said powder, and a control computer 8 in whichinformation is stored about a succession of cross-sections of thethree-dimensional product, which cross-sections build up thethree-dimensional product. During a work cycle, according to theembodiment shown, the work bench will be gradually lowered in relationto the irradiation gun after each applied layer of powder. In order tomake this movement possible, in a preferred embodiment of the invention,the work bench is arranged to be able to be moved in a verticaldirection, that is in the direction that is indicated by the arrow P.This means that the work bench starts in an initial position 2′ in aposition where a first layer of powder of the necessary thickness hasbeen applied. In order not to damage the underlying work bench and inorder for this layer to be of a sufficient quality, this layer is madethicker than other layers which are applied on top, whereby meltingright through of this first layer is avoided. Thereafter, the work benchis lowered in association with a new layer of powder being applied, tocreate a new cross-section of the three-dimensional product. For thispurpose, in an embodiment of the invention, the work bench is supportedon a stand 9 which comprises at least one rack 10 with teeth 11. Astepping or servo motor 12 provided with a cog wheel 13 sets the workbench 2 at the required height. Other arrangements known to experts inthe field for setting the working height of a work bench can also beused. For example, adjusting screws can be used instead of toothed cogs.According to an alternative embodiment of the invention, means in thearrangement for applying the powder can be gradually raised, instead oflowering the work bench as in the embodiment described above.

The device 28 is arranged to interact with the said powder dispenser forreplenishing it with material. In addition, the device 28 is arranged tosweep across the work surface in a known way by means of a servo motor(not shown), which moves the device 28 along a guide rail 29 which runsalong the powder bed.

Upon the application of a new layer of powder, the thickness of thelayer of powder will be determined by how much the work bench has beenlowered in relation to the previous layer. This means that the layerthickness can be varied as required. It is therefore possible, where across-section has a large change of shape between adjacent layers, tomake thinner layers whereby a higher degree of surface fineness isachieved and, when there is little or no change of shape, to make thelayers the maximum penetration thickness for the radiation.

In a preferred embodiment of the invention, the irradiation gun 6consists of an electron gun, with the means for guiding 7 theirradiation gun's radiation consisting of deflection coils 7″. Thedeflection coil 7″ generates a magnetic field, which guides theradiation generated by the electron gun, whereby melting of the surfacelayer of the powder bed in the required place can be achieved.

In addition, the irradiation gun comprises a high-voltage circuit 20which is intended to provide the irradiation gun in a known way with anacceleration voltage for an emitter electrode 21 arranged in theirradiation gun. The emitter electrode is connected in a known way to apower source 22 which is used to heat up the emitter electrode 21whereupon electrons are emitted. The function and composition of theirradiation gun is well known to an expert in the field.

The deflection coil is controlled by a control computer 8 according toan operating plan worked out for each layer that is to be melted,whereby guidance of the radiation according to the required operatingplan can be achieved.

In addition, there is at least one focusing coil 7′ which is arranged tofocus the radiation on the surface of the powder bed on the work bench.Deflection coils and focusing coils can be arranged in a plurality ofways known to experts in the field.

The arrangement is enclosed in a casing 15 that encloses the irradiationgun 6 and powder bed 2. The casing 15 comprises a first chamber 23 whichencloses the powder bed and a second chamber 24 which encloses theirradiation gun 6. The first chamber 23 and the second chamber 24 areconnected to each other via a duct 25, which enables emitted electrons,which have been accelerated in the high-voltage field in the secondchamber to continue into the first chamber in order to then strike thepowder bed on the work bench 2.

The powder dispenser 4 is arranged in such a way that it is in contactwith the surroundings by being partially arranged outside the casing 15and partially inside. A first part 4 a of the powder dispenser 4 isarranged in the first chamber 23 and a second part 4 b is arrangedoutside the casing 15. The powder dispenser 4 can be replenished inbatches or continually, without the casing 15 needing to be opened andthe manufacturing process being interrupted.

The supply of powder to the powder dispenser 4 can be carried out invarious ways. According to an embodiment (not shown in the figures), thepowder is supplied using a screw on the powder dispenser 4. According toanother embodiment (not shown in the figures), the powder is supplied tothe dispenser 4 via a container with movable compartments. The movablecompartments can be moved in such a way that an empty compartment can bemoved away from the dispenser opening and replaced by a fullcompartment, whereupon replenishing of powder to the dispenser 4 cancontinue.

In one embodiment, the first chamber is connected to a vacuum pump 26which reduces the pressure in the first chamber 23 to a pressure ofpreferably approx. 10⁻³-10⁻⁵ mBar. The second chamber 24 is preferablyconnected to a vacuum pump 27 which reduces the pressure in the secondchamber 24 to a pressure of approx. 10⁻⁴-10⁻⁶ mBar. In an alternativeembodiment, both the first chamber and the second chamber can beconnected to the same vacuum pump.

In order that the vacuum that has been created within the casing 15 bythe vacuum pumps 26, 27 will be retained or for there only to be aninsignificant increase in pressure, it is important for the powderdispenser 4 to have a column of powder 30. Any increase in pressure thatarises in spite of the column of powder 30 can be counteracted by thevacuum pumps 26, 27. The power that is required to counteract anincrease in pressure is typically of the order of 1/100 to 1/20 of themaximum power that is required to create the original vacuum in thecasing 15.

In addition, the control computer 8 is preferably connected to theirradiation gun 6 for controlling the emitted power of the irradiationgun and is connected to the stepping motor 12 for setting the heightposition of the work bench 2 between each consecutive application of alayer of powder, whereby the thickness of the individual layers ofpowder can be varied.

In addition, the control computer is connected to the said device 28 forapplying the powder onto the work surface. This device is arranged tosweep across the work surface, whereby a layer of powder is applied. Thedevice 28 is driven by a servo motor (not shown) which is controlled bythe said control computer 8. The control computer controls the length ofthe sweep and ensures that powder is replenished when required. For thispurpose, a load sensor can be arranged in the device 28, whereby thecontrol computer can obtain information to the effect that the device isempty.

FIG. 2 shows an arrangement 1 according to the invention viewed incross-section. The arrangement 1 according to FIG. 2 corresponds to thearrangement according to FIG. 1, with the exception that the arrangementin FIG. 2 has, in addition, a supply device 31 for supplying powder tothe powder dispenser 4 and a fixing device 32. The supply device 31consists of a container which is arranged above the powder dispenser 4.

FIG. 3 shows the arrangement 1 according to FIG. 2 viewed from the leftin FIG. 2. In other words, in FIG. 3 the arrangement 1 is rotatedthrough 90° to the right in relation to FIG. 2. The arrangement 1 inFIG. 3 is not shown in cross-section. The supply device 31 has a numberof compartments and is arranged to be able to move on a fixing device32. In this way, the supply device 31 can be moved from left to right,or vice versa, when a compartment is empty, in order to be able toreplenish the powder dispenser 4 from a full compartment.

The embodiment described constitutes only one example of how theinvention can be carried out. Other embodiments are also possible withinthe framework of what is described in the claims. For example, thearrangement can have more than one powder dispenser.

1. An arrangement for the production of a three-dimensional product,which includes a work bench on which the said three-dimensional productis to be constructed, a powder dispenser which is arranged to apply athin layer of powder onto the work bench to create a powder bed, anirradiation gun for transmitting energy to the powder so that melting ofthe powder takes place, the arrangement comprising: a casing withinwhich the pressure is reduced in relation to the atmospheric pressureand within which the work bench and the irradiation gun are located,wherein the powder dispenser is a continuous unit having a dispensingend and a powder refill end, where the dispensing end is disposed insidesaid casing and the powder refill end is disposed outside said casingsuch that a powder refill opening on the refill end is exposed to anambient atmosphere outside said casing and such that the powderdispenser is thereby directly accessible from outside the casing forrefill of powder material at any time during a production processwithout affecting pressure conditions inside the casing.
 2. Thearrangement as claimed in claim 1, wherein a column of powder in thepowder dispenser acts as a pressure barrier between the inside of thecasing and the environment outside the casing.
 3. The arrangement asclaimed in claim 2, wherein the column of powder has a height of 1000mm.
 4. The arrangement according to any one of the above claims, furthercomprising a first chamber, which encloses the work bench, and a secondchamber, which encloses the irradiation gun, the chambers being locatedinside the casing and connected to each other via a duct.
 5. Thearrangement as claimed in claim 4, wherein the powder dispenser isarranged in association with the first chamber.
 6. The arrangementaccording to claim 1, further comprising a supply device in the form ofa container with compartments which can be moved so that powder can besupplied to the powder dispenser from the different compartments.
 7. Thearrangement of claim 1, the irradiation gun comprising an electron gun.8. The arrangement of claim 1, wherein the powder refill openingincludes a cover with a valve arranged on top of said powder dispenser.